I like my LW conversion barrel well enough but If I was looking for a true upgrade over stock I would go KKM.
I have both a LW and a KKM barrel for the Glocks. I do notice a difference in better accuracy with the KKM barrel over the Glock and the LW. I had some functioning problems with the KKM barrel the first 100 rounds or so but after the barrel "seated, it function flawlessly and accuracy became apparent. The KKM barrel does have "tighter" chamber dimensions than the factory barrel, so if you're shooting reloads, make sure you're sizing correctly and test your rounds before loading large batches.
